Senate Judiciary Committee Chairman Chuck Grassley, (R) of Iowa (l.) and Sen. Patrick Leahy (D) of Vermont, the ranking member, with Sen. Dianne Feinstein, (D) of California, at far right, listen as Republicans and Democrats remain at an impasse over filling the US Supreme Court vacancy created by the death of Justice Antonin Scalia, during a business meeting on Capitol Hill in Washington, Thursday.

Since Supreme Court Justice Antonin Scalia passed away last month, both major political parties have been making preparations for a broad, expensive, and protracted political war over who will replace him. With President Obama expected to announce his nominee as early as this week, the Republican Party is ready to launch its first attack.

After a month of preparation, the GOP says it has prepared one of the most comprehensive judicial response efforts in its history, a multi-pronged campaign of attack ads, petitions, and media outreach that will target not only Mr. Obama's nominee, but some vulnerable Democratic senators as well.

The Democratic Party and a number of liberal advocacy groups have been making similar preparations for a month now. With Republican senators saying they won't hold a hearing for Obama's nominee until after the presidential election this November, in the hope that a Republican will win the White House and choose Justice Scalia's replacement, both sides are digging in for the long haul.

With the eight-person court now evenly divided between liberals and conservatives, Scalia's replacement could determine the Court’s political orientation for decades to come, with implications for the future on a range of issues, from climate change and gun rights to affirmative action and abortion. The stakes are high, and the political machines on both sides have responded accordingly, committing money and resources that are expected to make this fight the biggest political battle of the year outside the presidential election itself.

The Republican National Committee will contract with America Rising Squared, an outside group that specializes in targeting Democrats run by a longtime aide to Sen. John McCain (R) of Arizona. The party has already been conducting opposition research on Obama's short-list of nominees, and besides attacking the eventual nominee like they would a political candidate – with radio and digital attack ads, petitions, and research into their history – GOP officials will also be using the Supreme Court battle to target Democratic presidential candidates Hillary Clinton and Sen. Bernie Sanders, as well as Senate candidates in tough races in Colorado, Ohio, Florida, and Pennsylvania, among others.

The overriding message of the campaign will be that the nomination process should wait until after the election, to "make sure Democrats have to answer to the American people for why they don't want voters to have a say in this process," said RNC chairman Reince Preibus.

Across the aisle, Democrats have been engineering their own political campaign focused on ridiculing Republican obstructionism. Obama and his advisers have been strategizing with a broad coalition of liberal advocacy and lobbying groups since mid-February, The New York Times reported, with the groups "vowing to spend millions of dollars" on the campaign.

The Washington Post reported last month that the groups were also targeting Republican Senate candidates in tough races in Ohio, New Hampshire, and Wisconsin, among others, as well as writing op-eds, circulating petitions, and promoting the Twitter hashtag #DoYourJob, calling out Senate Republicans for refusing to hold nomination hearings.

"It's going to be the entire progressive movement up against the entire conservative movement," Frank Sharry, an immigration activist, told the Times in February. "I do think it's going to be a battle of a different order."